<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>req学习</title>
</head>
<body>
<form action="/req/demo3" method="get">
    提交用户名： <input type="text" name="username" value="zhangsan"> <br>
    <input type="submit"value="提交">
</form>
</body>
</html>